Combinatorial Cassettes for Higher-Throughput Screening of Osteogenesis
Carl G. Simon Jr., Subhadip Bodhak, Hariharan K. Iyer, Luis Fernandez de Castro Diaz, Pam Robey, Azusa Maeda, Sergei Kuznetsov
Animal models are the most biologically relevant method for measuring the osteogenic capability of bone graft formulations. However, animal experiments are slow, tedious and the results can be highly variable, even when conducted within the same lab. In order to begin to address these issues, a combinatorial cassette (combi-cassette) is presented for higher throughput screening of bone graft formulations in the mouse subcutaneous implantation model. Histology, X-ray microcomputed tomography and gene expression measurements demonstrated that 19 bone graft formulations can be tested in a single mouse, a 4.75-fold increase over the traditional approach of 4 implants per mouse. Osteogenesis in the combi-cassettes was statistically the same as that observed by traditional, non-combi methods. Both cell-based (primary human bone marrow stromal cell, hBMSC) and growth factor-based (bone morphogenetic protein-2, BMP-2) formulations were effective in the combi-cassettes. In addition, combi-cassettes enable implantation of positive and negative control formulations into every mouse. Further, multiple replicates of bone graft formulations may be implanted into each mouse, which enables the use of statistical analyses and the assessment of mouse variability. In conclusion, the combi- cassettes performed as well as traditional, non-combi approach. The increased sample size afforded by combi-cassettes may increase experimental throughput, reduce the number of animals required for testing, or provide replicates for statistical analyses and more reliable identification of osteogenic graft formulations.